This invention relates to the manufacture of rackets, and particularly to tennis rackets although the principles thereof are applicable to any type of strong racket, e.g. squash rackets.
Throughout most of the history of racket sports, all good rackets were made primarily of wood, generally in the form of a plurality of curved pieces laminated together by glue or the like. These rackets possessed many desirable qualities from the standpoint of strength, but also were subject to certain disadvantages. For example, wood is of variable quality at best, and wood of the best quality is increasingly scarce. In any event, wood is subject to warping and to fatigue, particularly under the stress of tightly stretched strings, and accurate control of weight, and especially of balance, was difficult.
Comparatively recently, the art has produced rackets wherein the frame is constructed of steel or aluminum. Obviously, a racket frame of such a material does not warp and possesses a very high degree of strength, but the initial cost of materials, as well as the cost of the equipment for forming the metal racket frames, is high, thereby making the consumer cost of such a racket high. Further, metal frames have problems of cracking of welds, and with physical properties of density, strength and stiffness tending to result in rackets which are too flexible.
The use of glass reinforced plastic materials has become widespread during this same period of time. It is well known that the glass reinforced plastics have a very high strength, they have a good modulus of elasticity, the raw materials are inexpensive, and they can be readily formed and otherwise handled. The use of glass reinforced plastic in a tennis racket frame was proposed as long ago as 1949, in Robinson U.S. Pat. No. 2,878,020. Yet in spite of this knowledge and early suggestion, the art has been unable to develop a satisfactory racket frame formed of fiber reinforced plastic material.